Endpoint Security ( Data security )

With endpoint security tools you are able to block the local ports and interfaces of the PC/Laptop. So, you are able to prevent data theft . But it is also possible to send the data via e-mail ( smtp or webmail ). To make the endpoint security more secure, you must find solutions to prevent the sending of emails.
I want to start here a discussion to find the best solution. Please tell me your suggestions and your ideas.